In an existing Long Term Evolution (LTE) time division duplex (TDD) system, seven different uplink (UL)/downlink (DL) subframe configurations are defined. “U”, “D”, and “S” in FIG. 1 are used to indicate subframe types. “U” indicates an uplink subframe, “D” indicates a downlink subframe, and “S” indicates a special subframe. In each configuration, 10 consecutive subframes form one radio frame. After obtaining a configuration type of a radio frame, user equipment (UE) can determine subframe types of various subframes.
With development of wireless network technologies, new services are emerging one after another, and different services have different resource requirements. This requires more efficient use of limited resources in future wireless networks. To achieve this objective, a dynamic time division duplex (D-TDD) technology gains increasing attention. The so-called D-TDD allows a network side to adjust an uplink/downlink subframe configuration more flexibly. An advantage is that the network side may dynamically adjust the uplink/downlink subframe configuration with a more refined granularity based on uplink/downlink resource requirements of different services, thereby achieving an objective of resource utilization optimization. Currently, the 3rd Generation Partnership Project (3GPP) has been formulating standards for a new radio access technology (NR) (also referred to as a fifth-generation mobile communications technology (5G)), and defines an importance of the D-TDD in the NR.
In discussions about the NR and the D-TDD, many companies have directly or indirectly expressed their opinions in supporting anchor subframes (or referred to as fixed subframes or non-dynamic subframes). An anchor subframe is a subframe in the D-TDD that is anchored and that does not allow a dynamic uplink/downlink change, and is used to transmit a necessary or important message in a system. For example, a DL anchor subframe (or a DL portion of an anchor subframe) may be used to transmit UE-common data, such as a synchronization signal, a system message, and a measurement reference signal, and a UL anchor subframe (or a UL portion of an anchor subframe) may be used to transmit information such as a physical random access channel (PRACH). FIG. 2 shows dynamic subframes and anchor subframes.
In discussions about the NR standards, it is already determined that a time-frequency resource that can be flexibly used shall be maximized as much as possible. From a D-TDD perspective, the time-frequency resource that can be flexibly used may be understood as a dynamic subframe different from the anchor subframe described above. An uplink/downlink attribute of the dynamic subframe is not anchored, and is configured dynamically by the network side depending on a requirement instead. This can greatly improve D-TDD flexibility and make an uplink/downlink attribute of the D-TDD meet various different service requirements in a more flexible and timely manner.
In a D-TDD scenario of the NR, subframe types of various subframes in the D-TDD cannot be properly determined based on the foregoing radio frame configurations.